HELP, how can my boyfriend become a citizen?

My boyfriend is French and I am American we have been dating for a year. I know he is the one, but being 22 its a bit early to get married. He has the equivalent of a B.A degree, and is very intelligent, charismatic,hardworking, and fluent in English and French.He wants to stay in the U.S. and work, how can this be achieved?Does anyone out there have other ideas then getting married. Thank you :)